Electric line switch



y 1966 D. H. CAMPBELL ETAL 3,250,882

ELECTRIC LINE SWITCH 7 Filed Aug. 26, 1964 INVENTORS. DUDLEY H. CAMPBELL J4ME5 F1 BULL/M4 United States Patent 3,250,882 ELECTRIC LINE SWITCH Dudley H. Campbell and James F. Sullivan, St. Marys, Pa., assignors to Stackpole Carbon Company, St. Marys, Pa., a corporation of Pennsylvania Filed Aug. 26, 1964, Ser. No. 392,180 4 Claims. (Cl. 200-157) This invention relates to electric line switches, and more particularly to finger operated trigger switches.

Some electrical accessories, such as hand-held electric drills, electric carving knives and other tools are energized by squeezing the pivoted trigger of an electric switch connected in the electric line of the tool.

It is among the objects of this invention to provide such a switch which is extremely simple in construction, which is composed of a minimum of parts, which is inexpensive, and which produces a wiping contact as the switch is closed and opened.

The preferred embodiment of the inventionis illustrated in the accompanying drawings, in which FIG.1 is a side view of our switch mounted in place;

FIG. 2 is a combined plan view and horizontal section of the switch;

FIG. 3 is an enlarged vertical longitudinal section of the switch taken on the line IIIIII of FIG. 2; and

FIG. 4 is a fragmentary cross section taken on the line IVIV of FIG. 3.

Referring to the drawings, an insulating base member 1 may be relatively long and narrow and provided at one end with a notch 2 (FIG. 2), when the base is designed for insertion in a slot in a tool housing 3. In such a case, a boss 4, in the housing can project into the notch to help hold the base in position. A fixed electric contact 5 is rigidly mounted on one side of the base near one end. A terminal 6 extends through the base and connects to the contact. Preferably, the two areintegral with each other and each helps hold the other in place.

For engaging this contact, there is a spring contact 8 formed from a resilient metal strip that extends lengthwise of the base. This strip has a mounting portion 9 spaced laterally from the fixed contact and located near the opposite end of the base. The mounting portion is secured to the base by any suitable means, such as by a rivet 10. As shown in FIG. 3, the major part of the strip extends from the rivet toward and across the fixed contact, but normally out of engagement with it. The free end of the strip, spaced outwardly from fixed contact 5, is connected to mounting portion 9 by an outwardly extending hump portion 11 having sides converging away from the base. At the opposite end of the mounting portion the spring strip is provided with a portion bent upon itself and extending outwardly away from the base, the outer end of this bent portion being in the form of a hinge loop 12. The end of the strip adjoining this bent portion extends through the base to form the second terminal 13 of the switch and. to help keep the strip from turning on the rivet.

An actuating trigger 15 for closing the switch is formed of any suitable material, such as a plastic, and is provided with a longitudinal closed-end channel 16 that faces base 1 and also receives hinge loop 12 and the hump portion 11 of the spring contact. The channel is long enough to extend across fixed contact 5. To pivotally connect the trigger to the base, a hinge pin 17 extends through the hinge loop and into the adjoining sides of the trigger at that end of the trigger. The hinge pin can be a roll pin that will hold itself in place in the hinge loop. The hump 11 of the spring contact engages the inner transverse wall' of the channel and normally spaces the free end of the trigger from the base as shown in FIG. 3. The free end 3,250,882 Patented May 10, 1966 ICC . trigger is swung toward the base by application of manual pressure it can move far enough to force the free end of the spring contact into engagement with the fixed contact to close the switch. Preferably, the portion of the trigger that engages the spring hump is inclined and engages the outer end of the side of the hump nearest the hinge.

Another feature of this invention is that after the spring contact has been moved into engagement with the fixed contact the trigger can still be swung a little further toward the base, which flattens the hump portion of the spring contact slightly and thereby causes its free end to slide against the fixed contact. When the trigger is released, the spring contact slides in the opposite direction across the fixed contact. This wiping engagement between the two contacts maintains their engaging surfaces clean.

A further'feat-ure of the invention is that the mounting portion 9 of the spring strip between the rivet and the adjoining side of the hump portion normally is inclined away from the base a few degrees, preferably about 9. The purpose of this to increase the effective length of the portion of the spring contact that moves toward and away from the base as the trigger is operated, and to provide an additional point of bending. If the relief angle were not present, the movable part of the spring contact would be analogous to a cantilever supported at its junction with the mounting portion of the strip. That would concentrate the bending at that junction. In the switch shown, the inclination of the mounting portion to the base reduces any such stress concentration by dividing up the bending of the spring contact between the area adjoining the rivet and the rest of the strip adjoining the raised end of the mounting portion.

The switch, as described this far, is complete and functions satisfactorily because the spring contact 8 will normally hold the'trigger in its outer position with the switch contacts separated. Nevertheless, for those who wish the trigger to have a more pronounced feel or resistance to closing movement, a coil spring 21 may be added to help hold the switch open while the trigger is released. This coil spring is compressed between the hump portion of the spring contact and the supporting base. To hold the coil spring in place, one or two of its convolutions adjoining the base are reduced in diameter and inserted in a small hole 22 in the base as shown in FIG. 3. The adjoining larger convolution is seated on the base.

It will be seen that in this switch a single metal spring strip serves not only as a movable contact, but also as a terminal, one part of the switch hinge, and the means by which the trigger is swung away from the base when released. This materially reduces the cost and complexity of the switch.

According to the provisions of the patent statutes, we have explained the principle of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

We claim:

1. An electric line switch comprising an insulating base, a fixed contact mounted on one side of the base and having a terminal extending through the base, a spring contact formed from a resilient metal strip having a mounting portion near one end spaced laterally from the fixed contact, means securing said mounting portion to said side of the base with the major part of the strip extending from the mounting portion toward and across the fixed contact normally out of engagement therewith, the strip at the opposite end of the mounting portion being provided with a portion bent upon itself and extending outwardly away from the base, the end of the strip adjoining said bent portion extending through the base to form a second terminal, the opposite free end of the strip being connected to said mounting portion by an outwardly extending hump portion having converging sides, the outer end of said bent portion being in the form of a hinge loop, a trigger provided with a longitudinal channel facing the base and receiving said loop and hump portion, the channel extending acrossthe fixed contact, and a hinge pin extending through said loop and the adjoining sides of the trigger at one end to permit the opposite end of the trigger to be swung toward and away from the fixed contact, said hump portion engaging the inner transverse wall of said channel and normally spacing said opposite end of the trigger from the base, and the trigger being movable toward the base far enough to force said free end of the spring contact into engagement with the fixed contact.

2. An electric line switch according to claim 1, in which said mounting portion of the strip between said securing means andthe adjoining side of said hump portion normally is inclined away from the base.

3. An electric'line switch according to claim 1, in which said free end of the spring contact engages the fixed contact before movement of the trigger toward the base is arrested, whereby further movement of the trigger tends to flatten said hump portion and thereby causes the free end of the spring contact to slide against the fixed contact.

4. An electric line switch according to claim 1, in which said base is provided with an aperture opposite said hump portion, and a coil spring is compressed between the hump portion and base, the baseend of the coil spring having a reduced diameter and projecting into said aperture to hold the spring on the base.

No references cited.

20 KATHLEEN H. CLAFFY, Primary Examiner. 

1. AN ELECTRIC LINE SWITCH COMPRISING AN INSULATING BASE, A FIXED CONTACT MOUNTED ON ONE SIDE OF THE BASE AND HAVING A TERMINAL EXTENDING THROUGH THE BASE, A SPRING CONTACT FORMED FROM A RESILIENT METAL STRIP HAVING A MOUNTING PORTION NEAR ONE END SPACED LATERALLY FROM THE FIXED CONTACT, MEANS SECURING SAID MOUNTING PORTION TO SAID SIDE OF THE BASE WITH THE MAJOR PART OF THE STRIP EXTENDING FROM THE MOUNTING PORTION TOWARD AND ACROSS THE FIXED CONTACT NORMALLY AND OUT OF ENGAGEMENT THEREWITH, THE STRIP AT THE OPPOSITE END OF THE MOUNTING PORTION BEING PROVIDED WITH A PORTION BENT UPON ITSELF AND EXTENDING OUTWARDLY AWAY FROM THE BASE, THE END OF THE STRIP ADJOINING SAID BENT PORTION EXTENDING THROUGH THE BASE TO FORM A SECOND TERMINAL, THE OPPOSITE FREE END OF THE STRIP BEING CONNECTED TO SAID MOUNTING PORTION BY AN OUTWARDLY EXTENDING HUMP PORTION HAVING CONVERGING SIDES, THE OUTER END OF SAID BENT PORTION BEING IN THE FORM OF A HINGE LOOP, A TRIGGER PROVIDED WITH A LONGITUDINAL CHANNEL FACING THE BASE AND 